DESCRIPTION

The main purpose of this utility is to recompress MNG files to get the smallest possible size.

Please note that this utility is not able to read a generic file. It´s granted to be able to read only the files generated by the AdvanceMAME emulator.

To compress the files this utility uses the following strategies:

•

Remove all ancillary chunks.

•

Use the MNG Delta feature to compress video clips with only small changes between frames.

•

Use the MNG Move feature to compress video clips with a scrolling background (option −s).

•

Reduce the color depth to 8 bit (option −r).

•

Use the 7zip Deflate implementation.

COMMANDS

−l, −−list FILES...

List the content of the specified files.

−z, −−recompress FILES...

Recompress the specified files. If the −1, −2, −3 options are specified, it´s used the smallest file choice from the previous compressed data and the new compression. If the −0 option is specified the file is always rewritten without any compression.

−x, −−extract FILES...

Extract all the .png frames in the .mng clips. You can use the −−shrink options to control the compression ratio of the .png files. The extracted images are always 24 bit images with alpha channel. You can remove the alpha channel with the −n option.

−a, −−add RATE MNG_FILE PNG_FILES...

Compress all the .png files on the command line as a .mng file. All the .png files must have the same size and the same bit depth. You must also specify an integer frame rate to use in the

OPTIONS

−0, −−shrink−store

Disable the compression. The file is only stored and not compressed. The file is always rewritten also if it´s bigger.

−1, −−shrink−fast

Set the compression level to "fast" using the zlib compressor.

−2, −−shrink−normal

Set the compression level to "normal" using the libdeflate compressor. This is the default level of compression.

−3, −−shrink−extra

Set the compression level to "extra" using the 7z compressor. You can define the compressor iterations with the −i, −−iter option.

−4, −−shrink−insane

Set the compression level to "insane" using the zopfli compressor. You can define the compressor iterations with the −i, −−iter option.

−i, −−iter N

Define an additional numer of iterations for the 7z and zopfli compressors for modes −3 and −4. More iterations usually give a better compression, but may require a lot more time. Try for example with 10, 15, 20, and so on.

−s, −−scroll HxV

The "−s HxV" option specifies the size of the pattern (H width x V height) used to check for a scrolling background. The size is expressed in pixels and it must be bigger or equal than the scrolling speed of the background. For example take the game 1942 that scrolls vertically by 1 pixel every frame. If you recorded with an interleave factor of 2 the vertical scrolling speed is 1*2 = 2. In this case the minimum pattern is "−s 0x2". Generally you can use "−s 8x8" and use bigger values only for games scrolling faster. If the game scrolls only horizontally or vertically you can speed up a lot the compression with monodirectional patterns like "−s 16x0" or "−s 0x16".

−S, −−scroll−square N

This option is like the option "−s NxN" but excludes big movement on both directions reducing the computation time. Specifically the check done is X+Y<=N.

−r, −−reduce

Force the color reduction to 8 bit. The reduction is really done only if any frame have less than 256 colors and if no alpha channel is present. To force the reduction also if an alpha channel is present use the −n option.

−e, −−expand

Force the color expansion to 24 bit.

−n, −−noalpha

Remove the alpha channel if present.

−c, −−lc

Force the use of the MNG LC (Low Complexity) specifications. It disables the delta compression. The file is always rewritten also if it´s bigger.

−C, −−vlc

Force the use of the MNG VLC (Very Low Complexity) specifications. It disables the delta compression and the precise timing. Warning! you may lose the correct timing information because the VLC format only supports integer frequency. The file is always rewritten also if it´s bigger.